<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<% pageContext.setAttribute("username", "pageContext"); %>
		<hr>
表达式\${pageScope.username}的值为：${pageScope.username} <br />
表达式\${requestScope.username}的值为：${requestScope.username} <br />
表达式\${sessionScope.username}的值为：${sessionScope.username} <br />
表达式\${applicationScope.username}的值为：${applicationScope.username}<br />

表达式\${username}的值为：${username}
<!-- 表达式${username}就是在 page、request、session、application 这 4 个作用域内按顺序依次查找 username
属性。 -->
</body>
</html>